Ramsey Electronics FX-440 User manual

SY THESIZED
F & PACICET DATA
UHF TRANSCEIVER
Y2
DIVIDE
BY
1024
U6
DIVIDE BY N
PROGRAMMING
PHASE
DETECTOR
11 Fun and Easy to build
11 Super easy alignment
us 07
LOOP
FILTER
DIVIDE BY
I 64/ss
I PRESCALER
U3
vco
SYNTHESIZED
OUTPUT
FREQUENCY
11 Covers 400 -480 MHz in 12.5 KHz steps!! ·
11 No crystals needed ... EVER!
111 Fantastic Packet rig with built-in Packet jack
111 True direct FM modulation for exceptional
audio and high speed data capability
Experience the satisfaction of operating
a rig that YOU built yourself!
440 MHz
MODEL FX-440

Ramsey Publication No.M440FX
Price$10.00
REFERENCE MANUAL AND
KITASSEMBLY INSTRUCTIONS FOR:
440 MHZ
AMATEUR PLL SYNTHESIZED
FM TRANSCEIVER
MODEL FX-440
400 -480 MHz
Published in Three Sections:
• FX-series General Reference Information
• Kit Assembly Phase
I: Circuit Stages A through F
• Kit Assembly Phase II: Circuit Stages G through T5<
Plus:
• Fold-out Schematic Diagram .
• Fold-out Multi-color Parts Layout Illustration
I RAMSEY I
RAMSEY ELECTRONICS, INC.
Amateur Radio and Hobby Kits Dept. 793 Canning Parkway
. .Victor, New York 14564 [phone] Fax: [phone]

A DEDICATION
The Ramsey FX-series FM Transceiver Kits are writing a truly NEW
chapter in the annals of the ham radio story. Growing numbers of today's
radio amateurs ARE willing to build, understand, adjust and maintain
modern VHF gear capable of digital frequency programming and data
communication
as well as FM voice. How do we know? We know it
because, during 1991, thousands of hams worldwide built and are using
our pioneering FTR-146 for two meters. The FX Transceiver design was
developed
in immediate response to those builders' suggestions, wish
lists and inquiries. This publication
is dedicated with deep thanks to all
those FTR-146 builders!
FX-440 VHF FM Transceiver Reference and Kit Assembly Manual
Ramsey Publication
No. M440FX First Printing: March 1992 Copyright
1992 by Ramsey Electronics, Inc. All Rights Reserved.
Revision number 1.2
Published by Ramsey Electronics,
Inc.
Printed in the United States of America
RAMSEY ELECTRONICS, INC.
793 Canning Parkway
Victor, New York 14564
Phone: [phone] Fax: [phone]

TABLE OF CONTENTS:
The Ramsey FX-440 Tranceiver Manual is organized into three sections:
General Reference Information, Kit Assembly Phase
1, and Kit Assembly
Phase 2. These three sections are bound together as a single volume.
FX-440 GENERAL REFERENCE INFORMATION
Notice Regarding FX-440 Frequency Coverage.............................. 4
FX-440 Technical Specifications..................................................... 5
Introduction to Transceiver
Kit Assembly........................................ 6
A Message to Ham Radio Beginners.............................................. 8
DC Power Supply Considerations................................................... 9
Enclosure and Hardware Considerations...............................
::~...... 10
Ramsey CFX Transceiver Enclosure Kit......................................... 12
Guide to PC-board
110 Connections............................................... 14
Microphone & Speaker Information................................................ 16
A Few Antenna Considerations...................................................... 16
UHF Packet Data Operation........................................................... 17
FX-series Transceiver Block Diagram............................................. 18
FX-440 Circuit Overview................................................................. 19
Quick-Reference Programming Guide............................................ 28
FX-440 Programming Worksheet.................................................... 32
Using Computer BASIC as a Programming Aid.............................. 33
How to Activate
an Auxiliary (non-Standard) Offset......................... 36
Programming "Minus• Offsets........................................................ 36
Basics of Externally-Controlled Frequency Switching...................... 38
FX-440 External Programming Basics............................................. 40
· FX-series GLOSSARY of Terms...................................................... 41
Troubleshooting Guide.................................................................... 46
Note on Replacement Parts............................................................ 48
FX-440 Master Component Index.................................................... 49
RAMSEY ELECTRONICS FX Kit Warranty Terms........................... 57
-KIT ASSEMBLY: PHASE 1
Assembly and Explanation of Circuit Stages A through F (including Kit
Parts List, kit building tips and preliminary receiver & VCO test)
FX Assembly 1: pages Assm. 1 to 41
KIT ASSEMBLY: PHASE 2
Assembly and Explanation of Circuit Stages G through TX (includes
all
Frequency Programming directions plus alignment and transmitter
! tuneup.)
FX Assembly 2: pages Assm. 42 to 78
FX-440
Ref. 3

IMPORTANT NOTICE
The Ramsey FX-440 VHF FM Transceiver is capable of
TRANSMITTING as well as receiving on any frequency in the
range of 400
to 480 MHz, making it suitable for a wide range
of
UHF communications requirements. Operation of the
Transmit function of this equipment requires
an appropriate
license issued by the Federal Communications Commission
(FCC) for the class of operation intended. The FCC issued
TECHNICIAN CLASS license or higher is required for
operation
in the Amateur 440 MHz band (420 to 450 MHz).
Proper licensing is required for MARS or CAP operations.
Amateur licensees
are required by the FCC to maintain strict
control over their equipment to prevent unlicensed operation
either
in the amateur band or outside it. FCC regulations
ENFORCE severe penalties for unlicensed operation of radio
transmitting equipment and for interference with other
communications services, whether malicious or accidental.
Ramsey Electronics, Inc. sells the FX-440 transceiver solely
for correctly-licensed operation. It is the sole responsibility of
builders and operators of this
RF electronics device, capable
of emissions controlled by FCC Rules, to understand and
comply with those rules.
. ,•''
Ref. 4 FX-440

SPECIFICATIONS FOR THE RAMSEY FX-440 440 MHz BAND
AMATEUR RADIO FM TRANSCEIVER:
General:
Frequency Range:
Tuning:
Programming:
Transmit Offset:
Mode:
Packet (Data} Operation:
Packet RX Audio:
Power Requirement:
Power Consumption:
Antenna Impedance:
Microphone Impedance:
T-R switching:
PTT circuit:
Semiconductors:
Transmitter:
Final Power Output
Final Output Stage:
Modulation:
Max frequency deviation:
Modulation distortion:
Receiver:
Circuitry:
Sensitivity:
Selectivity:
Squelch sensitivity:
Audio output:
Circuit access points:
FX-440
Any 20 MHz segment between 400 and
480 MHz
Diode-programmable PLL synthesis
12 front panel selected frequency pairs,
easily expandable by switches,
microprocessors, computers, etc. PLL
12.5 KHz steps with programmable offsets
Programmable: Simplex, + 5, -5, Aux
NBFM
All rates incl. 9600 baud . 5-pin DIN jack
(TXD, RXD, PTT, +12VDC, GND} I
Speaker, discriminator or true FSK
13.6V DC +/-10% (Negative ground}
1.0 A Transmit (for 3 watts RF output}
200 ma (Receive, no signal}
50 ohms
600 ohms or high impedance
PIN diodes
Solid State (for standard ICOM-type
speaker/mic connection}
10 IC's, 17 transistors, 24 diodes
(plus programming diodes}
2-4 watts RF
MRF630 or equivalent
True direct FM
+ /- 25 KHz, + /- 5KHz NBFM
Less than
5%
Double-conversion superhet
First IF: 21.4 MHz
Second IF: 455 KHz
12 db. SINAD less than 0.50 UV
± 7 KHz (-6db.}, ±15 KHz (-60db.}
Less than O. 25 uv
More than 2.0 watts
COR, RSSI, PL tone input, FSK demod.
+12V, + 8V, + 5V, PLL programming.
Ref. 5

INTRODUCTION
to FX-series VHF Transceiver Kit Assembly
For the 1990's, Ramsey Electronics has adopted a "Learn As You Build"
philosophy for ALL our electronics kits. We feel that licensed ham
operators should know about the equipment they
use, and also should
have the desire to understand how their gear works. Additionally, it has
been our corporate response to
all those urgings by public officials that
both students and their parents need to become sharper in science and
math. This •Learn
as You Build" approach to electronics hobby kits is
now evident
in all Ramsey Electronics build-it-yourself kits from our
under-$5 student kits up to this synthesized UHF transceiver suitable for
ham radio and public service applications alike.
We think that "learning (and UNDERSTANDING)
as we build" is
especially essential in a more sophisticated project such as the Ramsey
FX-series UHF transceivers.
In fact, we are so convinced of this basic
need that this kit instruction manual departs from the traditional scheme
of separating assembly directions from a "theory of operation.•
The FX-series of Ramsey VHF/UHF Transceivers puts today's FM 2-way
radio technology back
in YOUR hands at a budget price. Our idea of
"budget• looks far beyond the modest purchase price to our goal that
you can MAINTAIN your FX- unit
in good operating readiness with no
need for expensive shop service. On the other hand,
we also have made -
the transceiver design
as abuse-proof and rugged as possible.
•Alignment,• traditionally an intimidating many steps process is very
easy, quick and fool-proof in this circuit design.
Instead of separate stage-by-stage assembly directions plus separate
theory information, this
FX- instruction manual highlights your
transceiver's operational theory, often a single component at a time, with
actual construction steps provided
as follow-up after each explanation.
The assembly sequences are easy to find in the following pages. You
indeed have the freedom to solder first and read all about it later. We
hope, though, that you'll take it
easy, learning as you build, and then
enjoy the reliability of your Ramsey FX Transceiver for a long time to
come.
The "style" of our kit-building directions presumes that
you are peeking
at our multi-color parts layout sheet while seeing that the very same parts
outlines are imprinted
on the component side of your FX PC board. This
makes it very easy to properly place each and every component.
You'
II install EVERY FX- part perfectly by using our simple ste~by-step
kit building process. And you'll know the WHY of most assembly steps, if
not
all of them. Before you start, THINK about what you'll create from
those bags of parts
as a finished product! For a minimal investment of
your time
as well as your well-earned money, you will have a UHF FM
voice-data Transceiver that you will truly OWN. Real "owning• ultimately
means knowing how to maintain and understand something that we have,
in contrast to merely possessing a thing because
we spent the bucks to
do
so. You'll have the flexibility of 12 channels chosen by YOU with the
Ref. 6 FX-440

easy ability to change or expand. You'll have both FM voice and
high-speed data capability. When you're ready, you can experiment with
many different enhancements, concentrating
on those truly useful to you.
If there's ever a problem, you won't think twice about digging in and
fixing it. Whenever you decide you could use still another VHF/UHF
FM/data transceiver at a budget price, you' II know with confidence that
an FX-series kit is the right way to go.
What's faster: turning your FX- Transceiver to any one of 12 possible
channels programmed by
you, or trying to remember again eaxctly how
to use the memory pre-sets of your
HT, or your HF rig, or the VCR, or
the microwave?
Let's learn about and build up a
FX- VHF/UHF FM Transceiver!
FX-440 Ref. 7

A MESSAGE TO HAM RADIO BEGINNERS:
If you have just earned your Novice or Technician license, or are
studying for either of them right now, we'd like to say a special Thank
You for choosing this Ramsey VHF/UHF transceiver as part of your ham
radio beginnings. We have tned to make this instruction manual as clear
as possible. However, there are some VHF radio "basics" covered by the
FCC question pools for all ham license study guides that we must
presume that you have studied and understood. ·
Here is a simple guide to selected Technician Class questions to help
with any review you wish to make before building:
FCC Subelement 3AA (Selected Rules): 4.2 11-1.1 12.5 15.2
FCC Subelement 3AB (Operating Procedures): 2-1.1 2-1.2 2-1.3 2-1.4
2-1.5 2-2.1 2-2.2 2-3.1 3.2 6-3.1
FCC Subelement 3AC (Propagation): It's up to you to understand the
characteristic differences among HF (shortwave), VHF and UHF
communications.
FCC Subelement 3AD (Amateur Radio Practice): All of this is
fundamental know-how for hams.
In working on this project, be especially
familiar with:
1-1.1 1-1.2 1-1.3 7.1 9.1 through 9.5 (dummy loads)
FCC Subelement 3AE (Electrical Principles) 3AF (Circuit Components)
Please know ALL of this.
FCC Subelement 3AG (Practical Circuits): 4.21 FCC Subelement 3AH
(Signals and Emissions):
1.1 2-1.1 2-4.1 2-6.2 2-7.1 4.1 6-1.2
7-1.1 7-2.1 7-2.2
FCC Subelement 3AI (Antennas and Transmission Lines): You will WANT
to know all of this, if you don't want
to take all your savings from building
your own transceiver and spend it on a commercially-built antenna Very
good VHF antennas are easy and inexpensive to build yourself!
Ref. 8 FX-440

DC POWER SUPPLY CONSIDERATIONS
Your Ramsey FM Transceiver is designed to operate from any stable DC
voltage source in the 12 to 15 volt range, from typical car, boat or plane
12V systems to a wide variety of battery packs or AC-P9wered DC
sources. In a pinch, you can get on the air for quite a while with 8 to 1O
ordinary "D" cells! Our lab tests show only a .93 amp current draw for 3
watts of RF output. We have just a few points of advice and caution:
1. Your DC supply should be able to provide a minimum of 1.0
amperes in continuous service.
2. Any battery setup capable of supplying 12-1 SVDC will serve
quite
well.
3. Use of wall plug power supplies is NOT recommended.
Obviously, 12VAC output is not suitable. Most DC output
units do not have adequate voltage regulation.
4. Turn your transceiver OFF before re-starting the vehicle in
which it has been installed.
5. Replace F1 only with a 1 amp fuse.
6. If you power your transceiver from the +12V accessory
voltage available from other equipment, be sure that
source
is rated for the 1 amp required.
7. Your transceiver circuit includes noise suppression at the DC
input and additional filtering at the VCO, primarily to
prevent ignition/alternator noise from bein9 introduced into
the
FM modulation. If you hear ignition noise in the
receiver, the vehicle
has a serious general problem.
Check your transmitted signal on another receiver before
mobile operation. Radio Shack sells a variety of
noise-suppression capacitors
and chokes. The ultimate
solution, which has been tested, is to run the transceiver
from a smaller accessory battery.
If you plan to build a power supply for fixed-station use, there are
numerous construction articles
in ham and electronics hobby
publications. A convenient new book featuring easy-to-find components
and clear explanations
is Building Power Supplies (Radio Shack
276-5025.)
FX-440 Ref. 9

ENCLOSURE &HARDWARE CONSIDERATIONS:
The companion CFX case and knob kit is sold as a separate option
ONLY as an accommodation to those radio hams who have their own
ideas or resources for the "finishing touches.•
However, a proper case for your FX-series is much more than a
"finishing touch, " since the controls and jacks are panel mounted and
proper RF shielding is required.
The CFX case measures 9-3/4"L X 6"W X 1.5"H. 9"X6" dimensions are
minimum for accommodating the PC board. The height may vary if you
wish to include an internal speaker, accessory PC boards, additional front
panel controls or indicators, etc. If you are new at all this and do not
already own a suitable enclosure plus that collection of hardware and
knobs that every ham seems to accumulate, here is what you need to
know if you are hesitant to purchase the CFX case kit
A. •Blank" electronics enclosures have become among the most
expensive hardware in the industry, especially if you are buying
just one unit. This is because they are sold mainly to engineers
and designers for prototyping. A blank metal enclosure even
slightly comparable to the CFX case kit will run $30 to $80 or
more. Even a plain aluminum chassis box/cover will be around
$15.00.
8. If you think there's any chance you someday may wish to sell or trade
your transceiver, you should be aware that units mounted in odd
boxes may have even less value than the bare circuit board with
documentation alone.
C. Many distributors have a minimum mail order of $25.00.
D. Your best chance for finding an inexpensive alternative case is to
have access to a lot of ham friends who tend to •collect stuff,• or
to browse the catalogs or showrooms of electronic surplus
dealers. You just might find a ~orgeous new box originally
intended for somebody's ingenious Ultra Modem, external disk
drive or other dream gadget from two years ago.
Are we trying to discourage you? No, not really! We know you can see
that there are good reasons to consider calling Ramsey Electronics and
getting your CFX case
on its way while you work on the PC-board and
PLL Programming. However, we do not want you to feel "stuck" with our
recommended CFX enclosure, so we have worked up-a detailed
shopping list for getting what
you will need to make as attractive a
finished unit as possible with a single trip to the neighborhood Radio
Shack store.
Ref. 10 FX-440

Quantitv
RS Part No. Descri~tion 1992 Price
1
270-272174
Deluxe Project Enclosure
(two heights available) 10.79
1 set 274-section
Pkg. of 3 or 4 knobs 2.00-3.00
(styles vary)
1 set
270-201 Rub-on project labels 2.99
2 sets 276-195 PC-board standoffs/screws 2.38
This $16 to $18 (plus tax) in basic hardware also presumes availability of
all needed drill bits and/or a reamer or punches of sufficient size to make
the needed access holes for the rear panel jacks. You'll also want
to
figure on spray paint as well as a clear finish to protect the panel labels.
Tools and supplies, if not
on hand, could cost much more than the CFX
enclosure kit itself.
In addition, this style of case will have to be utilized upside-down and
also length wise rather than
as designed. This means that the top (black)
becomes the foundation for mounting the
PC board with the standoffs as
well securing the S0-239 antenna connector assembly. You may wish to
repaint the white bottom which now becomes the top. And, to use the
project labels (black lettering), you'll probably wish to repaint both pieces.
This adaptation of standard Radio Shack hardware
is adequate for indoor
or occasional use but not recommended for mobile operation. We are
happy to provide this
SUQgested alternative to the rugged case, knob and
hardware kit custom designed for the FX-series transceivers. The choice
is yours!
FX-440 Ref.
11

THE RAMSEY CFX TRANSCEIVER ENCLOSURE KIT
The CFX Kit is very obviously a fair value and solid investment for the
long term performance and worth of your transceiver. As we have
mentioned, we make it "optional" ONLY because some of our ham
customers have specialized applications requiring only the basic
PC
board kit. We try whenever we can to accommodate that important
do-it-yourself spirit of ham
radio.
ENCLOSURE KIT PARTS LIST
~ 11
Steel bottom shell with 5 threaded PC board standoff posts
Steel top shell
1 I I
~ 11
~ 11
Front control panel
Rear panel with access holes to PC mounted jacks
Steel side rails
PC board standoff spacers
#4 nuts to secure PC board on standoffs
#4 screws to mount front and rear panels
#6 screws for securing top and bottom to side rails
large knob for Channel Selection Switch
smaller knobs for Volume and Squelch controls
self-adhesive rubber feet
CFX CASE ASSEMBLY PROCEDURE:
The purpose of these hardware parts is largely self-evident. We offer the
following suggestions for your convenience and to minimize wear and
tear
on your factory-fresh CFX enclosure.
[ ] 1. Since the bottom shell might be used for several "test fittings"
during transceiver assembly, install the rubber feet right away to
protect its finish.
[ )
2. Obviously, the PC board cannot be secured permanently to the
bottom section until after installation of
L9 and L1OAFTER
Alignment and before Transmitter tuneup.
[ ]
3. Install the strain-relief grommet supplied with the transceiver kit in
its rear panel hole. Pass the black ground wire through this
grommet. The
red, fused wire will have to be unsoldered from S1
and then carefully resoldered after passing through the grommet.
Snap in the locking section of the relief grommet only AFTER both
the red
and black wires are in place.
[ ) 4. Remove the two screws from the S0-239 antenna connector,
gently bend the lugs as needed to match the rear panel holes,
then secure the jack and lugs to the rear panel.
[ ) 5. Since the top shell will not be needed until you're ready to go on
Ref. 12 FX-440

the air, keep it wrapped in protective material until you're really
ready to use
it.
[ ) 6. The side rails may be installed to the bottom section at any time.
To prevent loss of the screws for the
top, keep them loosely
threaded in the side rails.
[ ) 7. There is no point in securing the front panel controls and
jacks to the panel permanently until AFTER wiring the Channel
Selection switch. Note the locking hole for the switch in the front
panel which mates the tab
on the front of the switch.
[ )
8. Use care and a well chosen pair of pliers to secure the
microphone
and speaker jacks to the front panel, so as not to
scratch the panel.
[ ) 9. Bend the leads of the TX LED so that their tension presses the
front of the bulb against its front panel
hole.
[ ) 10. Whenever you find it necessary to remove the top shell, •store"
the screws back into their holes in the side rails.
[ )
11. If you decide to install a ribbon cable in the diode matrix for
external programming control, route the cable (folded
at a right
angle) on the synthesizer and receiver side of the board so that it
exits the case between the rear panel and top cover, right above
the
DC power cord. Do NOT route any such cable across the
VCO and transmitter side.
[ )
12. After the PC board is secured to the case bottom and fronUrear
panels, it is a good idea to neaten up the wires to the controls and
jacks, bundling them at two or three points with tie wraps or cord.
FX-440 Ref.
13

GUIDE TO PC BOARD 1/0 CONNECTIONS
" t:q ~
~~ ~~~0000000000
,. S::@f\:>-"'0<0m......im01.p..wro-
og; Q 0000000000000
-<
m
r
@5
:0
- 0
., z
I\) 0
(/)
.,,
0
~
ific
0 1
0 2
0.
0.
0 16
032
064
0128
02'<3
0512
01K
021<
041<
OSK
016K
0321(
O+RPT
O·APT
0 SIMP
o~
p
f
0
•
0
"0
32
0
..
0
128
0
256
0
512
0
1K
0
21(
0
41(
0
81<.
o~ ->-s:---~
l!!
Ref. 14
@
••R
o. 0
~
RF OUT
A
PACKET
o~ ~o o§
@
0 0
~ ~ C)
i5 "
0 0:::;:
:0
GROUND I
FX-440

GUIDE TO PC BOARD UO CONNECTIONS
In addition to primary interconnections required for jacks and controls,
etc., your FX-series Transceiver
PC board provides additional access to
operating voltages
and circuit features to make later customizing as neat
and easy
as possible. All these points are plainly marked on the board
itsel.f and highlighted on the facing page, with a few other components for
orientation.
1. PRIMARY CONNECTIONS:
PWR (near l20): + 12-15 volts DC from S1.
GROUND: - DC from battery or power supply.
SPEAKER: both connections near C37
MIKE: both connections (IN & GND) near notched end of U1
SQUELCH: two connections marked CW and W near C16
VOLUME: three connections marked IN, OUT, GND.
ANTENNA: Center of S0-239 connected at "RF OUT" near
C71
CHANNEL SWITCH: Row of holes numbered 1 through 12. The switch
wiper (moving contact)
is wired to + 5V near "1.•
EXT AUDIO: must be jumpered per options to enable pin 4 of J1.
2. TEST POINTS:
+ 12V, + av, + 5V, + aR, + aT permit checking for presence of those
voltages. +
aR = Receive mode. + aT = Transmit mode.
TP1: For checking of VCO control voltage during alignment.
TP2: For checking VCO frequency with counter.
TP3: For checking U3 prescaler output with counter.
R103: + 7VDC at top lead shows locked PLL. 0 volts = problem.
3. OPTIONS:
+ 12V, GND, +av, + 5V, + aT, + aR: provide supply voltage for
accessories or modifications designed by
you. + 5V is available
both near L1 and near
C102. + aT and, + aR are near 013, 014.
Jumper Options for Packet Operation: SPKR to
EXT AUDIO: Speaker
level audio for packet (J1). DISC to EXT AUDIO: FM discriminator
output for packet. FSK to EXT AUDIO: True FSK demodulation for
packet.
RSSI: "Received Signal Stren,gth Indicator" output from U1.
COR: "Carrier Operated Relay• output from U1.
PL: Input point for audio tones (DTMF, CTCSS, etc.)
Binary Programming Holes: The
row of holes alongside the Binary
Programming labels permits installation of ribbon cable for
external programming devices designed by the innovative amateur
radio community. switches or interfaces,
or a row of internal DIP
switches.
FX-440 Ref.
15

MICROPHONE &SPEAKER INFORMATION
The FX transceivers with the hardware supplied are designed to accept
standard ICOM or !COM-compatible speaker-mikes such
as MFJ-284.
The most conveniently available such unit
is Radio Shack No. 19-31 O,
new for 1992.
Be aware that the receiver audio amplifier
is capable of supplying a
husky 2 watts or more of audio power
and will drive full-size
communications speakers to excellent volume levels.
The··pn switching circuit can be activitated simply by intrcx:lucing a
resistance (e.g. 1
OK) from the microphone input to ground. This .
resistance
is enough to trigger the PTT circuit without interfering with the
microphone audio input.
Consider these factors
in selecting microphone, speaker and/or
speaker-mike for
FM voice operation. If your microphone and speaker
preferences differ radically from the use of a speaker/mike, and
you do
not wish to alter the front panel, remember that
you also have very easy
access to mike and speaker lines via
J1, the packet connector.
A FEW ANTENNA CONSIDERATIONS
The idea of building your own transceiver is to save money and enjoy
your hobby. Effective VHF
and UHF antennas are easy and inexpensive
to build, whether for fixed or mobile
use. There are plenty of off-the-shelf
antennas to buy, but don't hesitate to •roll your own.•
If
you are a newcomer to ham radio, you'll discover many strong opinions
about the "best" antenna to
use. A home-built ground plane vertical or
even a dipole can provide very satisfying results. Whether you need a
gain factor or directivity in your antenna depends
on your operating
goals. Regardless of the style of antenna, it really pays to give serious
attention to electrically-solid, weatherproof connections of the coaxial
cable to the antenna elements. A simple antenna
in gocx:l condition will
outperform a fancy one that's been neglected.
Popular ham magazines and ARRL publications provide plenty of
antenna building ideas. MFJ Enterprises offers
gocx:l value in simple
ready-to-use antennas for
440 MHz.
Ref. 16
FX-440

UHF PACKET DATA OPERATION
Your FM transceiver was planned and designed to accommodate easy
and reliable UHF packet radio operation.
The
J1 Packet 1/0 port can be quickly connected to many modern TNC's
and the Ramsey P-IBM or P64 Packet Modems with Radio Shack's
shielded DIN cable (42-2151). Otherwise, your first step is to prepare a
reliable 5-conductor cable with a 5-pin DIN plug (RS 274-003) at one end,
and the correct connector needed by your packet TNC at the other end.
If you salvage a "ready made" 5-pin DIN cable from something like a
discarded computer joystick, be sure that there are indeed 5 wires, or at
least the ones that are required by your TNC!
Consult your Packet TNC or Packet Modem documentation for ALL
details on hookup and operation. Pin 4 of J1 offers a choice of amplified
and squelched (speaker level) audio output, low-level (discriminator)
output, or FSK output. This choice is set up by the jumper wire positions
clearly visible on the PC board.
Packet RX Audio Jumper: Some TNC's require low-level audio from the
discriminator output of the FM detector, while others will accept speaker
output. Either is available in the FX transceivers. Simply install a jumper
in the appropriate location near VR1, to connect •EXT AU 010" to either
•SPKR" for speaker audio or •DISC" for discriminator audio. Use scrap
resistor wire to make the jumper. You also can choose to wire these
three points to a miniature SPOT switch which you can mount on the rear
panel near the packet connector. OR, use a PC mount switch in the
jumper area itself. Provision
is also made for true FSK output (near C7)
from pin 14 of U1, which may be required by some high baud rate
TNC's. Use a short length of hookup wire from FSK to EXT AUDIO.
Use this space to diagram your TNC cable connection:
+12v PACKET
- FSK
EXT AUo-Dl_O -~-+--+--t--t---+--i-<;
~1sc./
_,,,,/JUMPER
-
SP-KR
PACKET JACK
0 0
3 5 2 • 1
FX-440 Ref.
17

Y2
c::::J
RAMSEY FX-SERIES FM TRANSCEIVER
(With emphasis on the PLL and VCO)
LOCK
DETECT
DIVIDE U5:A
07
PHASE
BY
LOOP vco
DETECTOR
FILTER
1024
I
DIVIDE BY
-=
Ref. 18
U6
PROGRAMMING
Q3
RECEIVE
PRE-AMP
TXIRX
Pt>l SWITCH
06. D7
02,017
RECEIVE
PRE-AMP
+aV RECV
+aVXMIT
64/65
PRESCALER
lJ3
MC3335 (U1)
DUAL CONVERSION
FM RECEIVER IC
LM3BO (U2)
AUDIO
AMPLIFIER
PTT
U.-C,D
012-01-4
SYNTHESIZED
OUT PVT
FREQUENCY
018
vco
BUFFER
010
TRANSMIT
BUFFER
MIKE
AMP
U.-A,B
MICROPHONE
FX-440